Backup control for HVAC system

Abstract

An equipment interface module that can operate one or more pieces of HVAC equipment in accordance with instructions received from a properly operating thermostat, yet can also operate the HVAC equipment when communications between the thermostat and the HVAC controller are lost due to, for example, low battery power at the thermostat, malfunctioning thermostat sensor(s), malfunctioning communication and/or thermostat circuitry, electrical interference, and the like. In some instances, the equipment interface module may regulate the HVAC equipment in accordance with a signal from a remote sensor when communication with the thermostat is lost.

1. An HVAC system comprising:
 an HVAC component having an HVAC controller, wherein the HVAC component includes a forced air HVAC unit having a circulating blower; 
 a remotely located wireless thermostat; 
 an equipment interface module in communication with the wireless thermostat, the equipment interface module configured to provide instructions to the HVAC controller in response to signals received from the wireless thermostat; 
 a remote sensor that is in communication with the equipment interface module, the remote sensor providing the equipment interface module with a control signal related to an environmental parameter within a building; 
 wherein the equipment interface module is also configured to provide instructions to the HVAC controller without input from the wireless thermostat if the equipment interface module loses communication with the wireless thermostat, and the equipment interface module is configured to activate the circulating blower in order to move air past the remote sensor after the equipment interface module loses communication with the wireless thermostat. 
 
     
     
       2. The HVAC system of  claim 1 , wherein the equipment interface module operates the circulating blower continuously until communication is restored between the equipment interface module and the wireless thermostat. 
     
     
       3. The HVAC system of  claim 1 , wherein the equipment interface module operates the HVAC component in accordance with a predetermined temperature setpoint if communication is lost between the equipment interface module and the wireless thermostat. 
     
     
       4. The HVAC system of  claim 1 , wherein the wireless thermostat comprises a battery, and communication between the equipment interface module and the wireless thermostat is lost as a result of the battery having insufficient energy to operate the wireless thermostat. 
     
     
       5. The HVAC system of  claim 1 , wherein the wireless thermostat comprises an RF transmitter and the equipment interface module comprises an RF receiver. 
     
     
       6. The HVAC system of  claim 1 , wherein the forced air HVAC unit comprises a furnace. 
     
     
       7. The HVAC system of  claim 1 , wherein the forced air HVAC unit comprises an air conditioner. 
     
     
       8. The HVAC system of  claim 1 , wherein the remote sensor comprises a return air temperature sensor disposed in a return air duct of the HVAC system. 
     
     
       9. The HVAC system of  claim 1 , wherein the remote sensor comprises a sensor that is wired to the equipment interface module. 
     
     
       10. The HVAC system of  claim 1 , wherein the remote sensor comprises an outdoor air sensor. 
     
     
       11. The HVAC system of  claim 1 , wherein the remote sensor comprises a humidity sensor and the equipment interface module is configured to operate the HVAC component to control a humidity level if communication is lost between the equipment interface module and the wireless thermostat. 
     
     
       12. The HVAC system of  claim 1 , wherein the equipment interface module is configured to store equipment configuration information previously provided by the wireless thermostat. 
     
     
       13. The HVAC system of  claim 12 , wherein the equipment interface module is configured to provide instructions to the HVAC controller, in the absence of communication with the wireless thermostat, in accordance with the stored equipment configuration. 
     
     
       14. A method of operating an HVAC system comprising an HVAC component and an HVAC controller, a wireless thermostat, an equipment interface module and a return air sensor disposed in a return air duct of the HVAC system, the method comprising the steps of:
 operating the HVAC component in accordance with instructions received from the wireless thermostat, wherein the HVAC component comprises a forced air HVAC unit having a blower; 
 detecting if communication between the wireless thermostat and the equipment interface module fails; and 
 controlling the HVAC component via the equipment interface module and the return air sensor until communication between the wireless thermostat and the equipment interface module is reestablished, wherein controlling the HVAC component via the equipment interface module and the return air sensor includes:
 operating the blower; 
 monitoring a return air temperature via the return air sensor; and 
 controlling the HVAC component to achieve a desired return air temperature. 
 
 
     
     
       15. The method of  claim 14 , wherein the equipment interface module operates the HVAC component in accordance with a predetermined temperature setpoint after communication is lost between the equipment interface module and the wireless thermostat. 
     
     
       16. An equipment interface module configured to communicate with a wireless thermostat, and a return air sensor that is disposed in a return air duct of an HVAC system, the equipment interface module configured to provide instructions to an HVAC component that includes a circulating blower in fluid communication with the return air duct, the equipment interface module comprising:
 an RF receiver; and 
 a controller that is configured to:
 recognize if communication between the wireless thermostat and the equipment interface module is lost; 
 start the circulating blower after communication is lost; 
 monitor a return air temperature in the return air duct via the return air sensor; 
 operate the HVAC component in accordance with a signal from the return air sensor to achieve a desired return air temperature until communication between the wireless thermostat and the equipment interface module is restored. 
 
 
     
     
       17. The equipment interface module of  claim 16 , wherein the controller operates the HVAC component in accordance with a predetermined temperature setpoint after communication is lost between the equipment interface module and the wireless thermostat. 
     
     
       18. The method of  claim 16 , wherein the blower is operated continuously until communication is restored between the equipment interface module and the wireless thermostat.